May 2004
Soil Liquefaction
Undergraduate Research
Developed by: Alisha Kaplan
Under Direction of: Dr. Paul Mayne
Mid-America Earthquake Center and
Georgia Institute of Technology
What is Soil Liquefaction?
During heavy ground shaking by earthquakes, liquefaction occurs when the pressure
exerted by the water present in saturated soil becomes so great that the soil particles
become ‘suspended’ in the water. A soil deposit that is liquefied behaves like the better
known phenomena: quicksand.
A few key terms:
 Saturated soils: soils in which the space (voids) between the soil particles is
completely filled with water
 Pore water pressure: pressure exerted on particles of soil by the water in the
voids. Most of the time this pressure is relatively low (hydrostatic) and results in
an equilibrium condition of effective stress state. However, there are some
circumstances in which rapidly increased stresses can cause the pore water
pressure to increase.
In more technical terms, liquefaction is imminent when the porewater pressure (u) equals
the total overburden stress (vo). This creates an effective stress state equal to zero (vo'
= [vo – u] = 0).
Due to the forces exerted by gravity, soil
particles naturally rest upon each other
and, depending on the properties of the
soil, form sort of grid that is relatively
stable (or can be made so by compaction
or other construction practices). During
liquefaction the water pressures become
high enough to counteract the gravitational
pull on the soil particles and effectively
‘float’, or suspend, the particles. The soil
particles can then move freely with respect
to each other. Since the soil is no longer
Nigata, Japan, 1964
behaving as an inactive grid of particles, the
strength and stiffness of a liquefied soil is significantly decreased, often resulting in a
variety of structural failures. (The picture at right shows overturned apartment buildings
in Niigata, Japan due to liquefaction in 1964. Picture
below shows an example of lateral spread failure due
an earthquake in Kobe, Japan in 1995.)
Typically when we discuss liquefaction due to a
seismic event, we are addressing “cyclic
liquefaction”, which occurs when repeated cycles of
shearing generate an accumulation of porewater
pressures. However, if the soil is very loose sand,
“flow liquefaction” can occur from first time loading
during site development. Also, “quasi liquefaction”
Kobe, Japan, 1995
describes a state of partial liquefaction of a soil deposit that does not propagate fully
throughout the site, however the subsurface liquefaction response still negatively affects
structures at the surface.
If liquefaction occurs beneath a surface that
has hardened as a result of compaction,
weathering, or some other process; ‘sand
boiling’ can occur. The water pressures build
below the surface to the point that the water
breaks through the solid surface much like a
bubble in boiling water. The pictures at left
and below illustrate craters left behind as
evidence of sand boiling.
On the US West Coast, these sand boils are
normally about one to three feet in diameter
(0.3 to 1 meter), see photos at left and below
right. In the New Madrid Seismic Zone, the
level of sand liquefaction was so extensive
that the sand boils in this region are called
“sand blows” since they generally are 10 to
100 feet diameter (3 to 30 meters).
Olympia, Washington, 2001
Loma Prieta, 1989
New Madrid Seismic Zone
What is Soil Liquefaction? (cont’d)
Figure 1
Figure 2
Figures 1 and 2 show a typical view of soil grains in an
unexcited, saturated deposit. The blue column on the
right indicates the magnitude of porewater pressure
present. The arrows in Figure 2 indicate the forces
created by the interactions of the soil grains. Figure 3
shows elevated water pressure created by additional
loading (as from a seismic event. The increased water
pressure acts to ‘float’ the grains and thereby decreases
the interaction between grains, thus causing the
characteristic properties of liquefaction.
[Figures
referenced from The Soil Liquefaction web site
maintained by the Civil Engineering Department of the
University of Washington. See sources for specific
information.]
Figure 3
Fielding Lake, Alaska, 2002
What affects whether or not soil liquefaction will occur?
A deposit of soil, by nature, is able to be
compacted through the rearrangement of the
particles within; but, water is incompressible
as a property. As a result, any increase to the
stress acting on a saturated soil-provided it
occurs rapidly enough and is large enough to
completely overcome the resistance
presented by the structure of the soil-will
cause the water to act alone in resistance and
frees the soils to move against each other
Izmit, Turkey, 1999
easily thereby lowered the strength and loadbearing capabilities of the soil (damage to a structure
during the 1999 earthquake in Izmit, Turkey is shown
above). Thus the phenomena of soil liquefaction is
created. Liquefaction is most often known as the result
of a major earthquake, but can also be caused by
construction practices such as blasting, vibroflotation
and dynamic compaction.
Because soil must be saturated for liquefaction to
Lake Merced, California, 1957
occur, it is observed most often in areas of low
elevation near bodies of water. It should be noted that
this can occur easily on river banks as well as near
larger bodies of water (pictures at right show sliding in
1957 on the banks of Lake Merced, California, above,
and below in 1976 in Guatemala on the Montagua
River). Liquefaction can also occur in soil that is
completely submerged and commonly causes
significant damages to bridge foundations, off-shore
oil drilling facilities, and other structures that are
supported by submerged soil deposits.
Port Island, Kobe, Japan, 1995
Montagua River, Guatemala, 1976
Generally, liquefaction will occur in loose clean to silty
sands that are below the groundwater table but still
close to the surface of the deposit. Historically, these
sands are young Holocene age geomaterials. Below
depths of approximately 20m, we generally do not see
any evidence of liquefaction. This is due to the fact
that deeper soils become compacted by the weight of
the soil layer above. In the left image lateral
displacement and failure of a quay wall on Port Island,
Japan in 1995 can be seen.
Why is liquefaction important?
Seismic events, in general, can cause a number of
dangerous ground conditions that can lead to structural
damage and failure resulting in loss of life. Severe
ground shaking, lateral spreading (such as landsliding
and deposit movement/shifting), as well as
‘incoherence’. Incoherence is the propagation of a
Niigata, Japan, 1964
wave in a structure causing foundation or bridge piers
to experience movement that is out of sync with the rest
of the structure (see bridge failure from 1964
Earthquake in Niigata, Japan, right, and upper deck
collapse of Bay Bridge from San Francisco, California
1989, left). Liquefaction may amplify the potential for
those conditions and the damage they cause.
Loma Prieta, California, 1989
Liquefaction is responsible for extreme property
damage and loss of life due to a several variations of
failure potential. Liquefied ground is no longer stable
to withstand the stresses it is subject to from structural
foundations or even its own weight, leading to a variety
of potential failures. The witnessed effect on structures
with their foundations in a liquefied deposit resembles
quicksand with a bearing capacity failure occurring
beneath the foundations. The building structures will
lean and fall; or at times even split open under the
strains (see pictures below of structural damage caused
by 1999 earthquake in Izmit Turkey).
Izmit, Turkey, 1999 (both images)
Also, dams and retaining walls are common boundaries to many major bodies of water
and their adjacent shores. Both rely on the strength and stiffness properties of soil for
their stability. The failure of the soil around them not only can cause the structure itself
to weaken, lean, and possibly even fall; but also can result in ‘subsurface landslides’,
during which the supporting soil at the base of the dam or wall loosens and slides out.
Dam and retaining wall failure are especially problematic concerns due to the additional
potential for flooding.
The damaging effects of liquefied
soils are not only visible in the
structural chaos left behind. The soil
itself can be weakened and fail due
to its own weight. Often, erosion
from rivers and streams cuts into the
soil along their banks, leaving behind
scoured ground and gullies. The
stresses produced during liquefaction
can cause tension cracks to form in
the soil near the embankment, or it
can collapse altogether, commonly
known as lateral spreading or
landsliding. Soils on or near slopes,
hills, or mountains can experience
the same effects.
Olympia, Washington, 2001
Lateral spreading during the Kobe earthquake in Japan
in 1995 caused the paved surface shown in this picture
to fall 1-1.2 meters below original grade. Local
flooding occurred as a result.
Kobe, Japan, 1995
How can the risk of damage due to soil liquefaction be reduced?
There are several ways in which risk and severity of damage as a result of soil
liquefaction can be reduced. The first and most obvious is, to avoid planning
development on liquefaction susceptible soils. Besides in-situ testing, vulnerable sites
can also be identified by researching any prior events at the site. Maps showing sites of
prior liquefaction can be located from many government and research entities. See links
to SIM 2822: Surficial Geologic Map of the Southeast Memphis Quadrangle, Shelby
County, Tennessee and SIM 2823: Surficial Geologic Map of the Southwest Memphis
Quadrangle, Shelby County, Tennessee, and Crittenden County, Arkansas, included in
the information resources on page 10.
If it necessary to construct on liquefaction
susceptible soils, one can modify the design of a
structure in several ways to make the structure
more resistant damage potential from liquefaction.
A structure that incorporates ductility, has
supports that are adjustable to accommodate
differential settlement, possesses the ability to
accommodate large deformations, and has a
foundation design that can span ‘soft’ spots, can
all decrease the amount of damage incurred in the Example of foundation design that
case of a liquefaction event.
spans over a soft spot
In addition to designing a liquefaction-resistant structure, steps
can be taken to improve the soil conditions and lower the
potential for liquefaction occurrence. A variety of ground
modification techniques are available to change the ground
conditions. Methods that increase soil drainage and density can
lower liquefaction risk. These include: vibroflotation; vertical
wick drains; dynamic compaction; installation of stone columns,
compaction piles, and compaction grouting; and use of various
drainage improvement techniques are all acceptable options.
Dynamic compaction
Injection & grouting
Where can I find more information?
Liquefaction information can be found in a number of sources: websites, articles in
professional journals, and books. Some identified sources are listed below, but to ensure
the information is most up-to-date and applicable to your needs, use these resources as a
starting point to do some research of your own.
Sources used in this paper
http://www.liquefaction.com/
Site maintained by Dr. Richard Olsen from USAE of waterways experiment station with
links to pages on “Evaluation of Earthquake Induced Soil Liquefaction”, “Links and
Information for the Geotechnical Cone Penetrometer Test”, “Geotechnical Engineering
Information”, and “Geotechnical Web Site Links”
http://neic.usgs.gov/neis/new_madrid/new_madrid.html
Collection of New Madrid Information by USGS
http://mae.ce.uiuc.edu/
Mid-America Earthquake Center
http://www.nees.org/
Network for Earthquake Engineering Simulation
http://www.ce.washington.edu/~liquefaction/html/main.html
Site maintained by the civil engineering department at the University of Washington.
“The Soil Liquefaction web site was developed to provide general information for
interested lay persons, and more detailed information for engineers. Visitors who are not
familiar with soil liquefaction can find answer to typical questions.”
http://www.eeri.org
Homepage for the Earthquake Engineering Research Institute
http://www.ce.gatech.edu/~geosys/Faculty/Mayne/papers/index.html
An index of research papers written by my advisor, Dr. Paul Mayne, in conjunction with
the Mid-America Earthquake Center and Georgia Institute of Technology.
http://www.bfrl.nist.gov
National Institute of Standards and Technology – Building and Fire Research Laboratory
http://geoinfo.usc.edu/gees/
Geotech Earthquake Engineering Server
http://earthquake.geoengineer.org
Geotechnical Earthquake Engineering Portal
http://pubs.usgs.gov/sim/2004/2822/
SIM 2822: Surficial Geologic Map of the Southeast Memphis Quadrangle, Shelby
County, Tennessee
http://pubs.usgs.gov/sim/2004/2823/
SIM 2823: Surficial Geologic Map of the Southwest Memphis Quadrangle, Shelby
County, Tennessee, and Crittenden County, Arkansas
Some Seismic Site Analysis Software Available
There are some softwares available that can lend a hand when characterizing a site’s
seismic risk. Below is a list of programs found during the course of this research and
some basic information about the program itself and its availability. (Note that 1D, 2D,
and 3D are modeled with time input as well and thereby can also be called 2D, 3D, and
4D.)
SHAKE2000
Windows compatible 1D analysis of site-specific response and the evaluation of
earthquake effects on soil deposits. Integrates former program entities ShakEdit and
SHAKE. One-user license costs $250. See www.shake2000.com for more information.
Rockware Visual Seismic (Version 3 – 10/03)
Developed by Rockware Inc. 2D, 3D, and 4D seismic and GPR visualization and
interpretation. Demo available, full version available for $1995.
http://www.rockware.com for more information or downloadable demos.
SEM2DPACK
2D Spectral Element Method code (in Fortran 95) and utilities for the study of seismic
wave propagation in sedimentary basins and earthquake dynamics. Current version is
2.2.1. Available freely for research purposes.
http://geoweb.princeton.edu/people/resstaff/Ampuero/software.html
IASPEI Seismological Software Library
The International Association of Seismology and Physics of the Earth's Interior (IASPEI)
is a nonprofit professional association dedicated to furthering the knowledge of
seismology and solid-earth geophysics. In 1988, IASPEI established a Working Group on
Personal Computers to promote the sharing of seismological software. Under the auspices
of the Working Group and in collaboration with the Seismological Society of America
(SSA), a series of seismological software volumes for IBM-compatible personal
computers is being published with W. H. K. Lee as editor, and J. C. Lahr and F.
Scherbaum as associate editors. The editorial board is chaired by Hiroo Kanamori and
includes R. D. Adams, V. Cerveny, E. R. Engdahl, Y. Fukao, R. B. Herrmann, E. Kausel,
V. Keilis-Borok, B. L. N. Kennett, and S. K. Singh. So far, six volumes of the IASPEI
Software Library have been published. Each volume includes the executable code and
examples on floppy diskettes, and printed documentation (for IBM-compatible PC's
only). Volume 1 (first edition 1989; second edition 1994) contains programs for realtime seismic data acquisition, processing, and analysis. It includes a description of the
hardware implementation for a PC-based seismic system and programs to perform
seismic data acquisition, interactive picking of seismic phases, filtering, spectral and coda
Q analysis, and earthquake location. At present, about 150 seismic networks using
Volume 1 software are in operation worldwide. The second edition of this volume
contains revised software and several new programs, and supports USGS digital
telemetry standards and PC-SUDS format. Volume 2 (first edition 1990; second edition
1994) is a companion to the first volume. It contains twelve computer programs for
plotting seismic data on the monitor screen and generating a hard copy. It includes a 3dimensional data-viewing program for rotating, enlarging, or shrinking objects and data
points. The second edition of this volume contains several new programs for plotting
seismic waveform data in the PC-SUDS format. Volume 3 contains two major
programs: (1) SeisGram by Anthony Lomax for interactive analysis of digital
seismograms, and (2) SYN4 by Robert McCaffrey, Geoffrey Abers, and Peter Zwick for
inversion of teleseismic body waves. This volume (published 1991; updated in 1994 to
support the PC-SUDS format) is a toolbox for seismological research, especially on
broad-band digital seismic data. Volume 4 is a toolbox for managing bibliographic
information and includes programs to automate reference preparation in manuscripts and
to manage a user's own references. It includes a searchable database of all articles
published in the Bulletin of the Seismological Society of America from 1911-1993 and
some frequently cited articles for seismologists. Volume 5 is a programmable interactive
toolbox for seismological analysis (PITSA) by Frank Scherbaum and James Johnson, and
includes a short course on "First Principles of Digital Signal Processing for
Seismologists." The manual and PC-version code was published in 1992. A version of
PITSA for Sun workstations is available from the IRIS Data Management Center, Attn:
Tim Ahern, 1408 NE 45th Street 2nd Floor, Seattle, WA 98105; telephone (206) 5470393. Volume 6 is called "Algorithms for Earthquake Statistics and Prediction" and
contains three software packages: SASeis, M8, and UpDate. SASeis contains ten programs
for statistical analysis of seismicity. M8 is an algorithm using pattern recognition
techniques for earthquake prediction, and UpDate is an algorithm to aid in the
preparation of input data for M8. Cost is $250 for each volume. See
http://www.seismosoc.org/publications/IASPEI_Software.html for more information.
Additionally, ORFEUS Seismological Software Library: PC-software links contains links
for many seismological freeware programs and is kept quite up to date.
http://orfeus.knmi.nl/other.services/pc_software.links.shtml
And, an extensive listing of Earth Science software applications to meet various needs,
including seismic modeling, is available at
http://www.esinfo.com/earthscience/branches/applicat.htm with useful reviews of the
softwares listed. However, many of the links are no longer current, so some searching
may be required to find the newest locations of the programs selected.
Acknowledgements
The Mid-America Earthquake Center at University of Illinois Urbana-Champaign
provided funding for this semester of undergraduate research under project HD-7 at
Georgia Institute of Technology. Dr. Paul Mayne sought out the funding and directed the
progress of the project and thus made the development of this paper possible.